Method and apparatus for forging



Dec, 18, 1962 s. J. VICKERS 3,069,535

METHOD AND APPARATUS FOR FORGING Filed May 14, 1959 2 Sheets-Sheet 1FORG\NG STATION \2 WATER SUPPLY POWER SUPPLY sENsmG DEVKIE 29 HEN NE;STATION INVENTOR. STANLEY .I VICKERS BY WMM PREPARAT\ON STA \O Dec. 18,1962 s. J. VICKERS 3,

METHOD AND APPARATUS FOR FORGING Filed May 14, 1959 2 Sheets-Sheet 2"fig: 2 F 23 INVENTOR. STANLEY J: VICKERS United States Patent 3,069,535METHGD AND APPARATUS FQR FORGKNG Stanley J. Vicirers, Palos Park, IlL,assignor to American Brake Shoe Company, New York, N.Y., a corporationof Delaware Filed May 14, 1959, Ser. No. 813,143 5 Claims. (Cl.219-154-) This invention relates to a new and improved method of forgingand to apparatus for carrying out that method. More specifically, theinvention relates to a new and improved forging method in which thebillet or other metal piece, usually steel, being forged is speciallyheated before forging, and to a particular form of electrical apparatusemployed therefor.

In a conventional forging operation, whether carried out by a press, ahammer, or an upsetter, the billet to be forged is first heated to arelatively high temperature, just short of the melting point, in afurnace. With steel billets, and also other metals, the preheatingusually forms a relatively heavy scale upon the billet which interfereswith the degree of precision to which the forging can be held. In fact,the thickness of the scale becomes the effective limit on tolerances towhich the forging may be held. Moreover, extended periods of time arerequired to assure uniform throughout the billet, since the center ofthe billet is not heated directly, but rather is heated only byconduction from the surface. indeed, even relatively long periods ofpreheating in conventional furnace arrangements may still fail toachieve uniform heating throughout the billet, with the result that theforging may be defective. Conventional methods are also difficult toadapt to automatic handling of the billets, barring the use of extremelylong furnaces, and present substantial problems in instances in which itmay be necessary to change the temperature to which the billets areheated before forging, as when there is a change in the kind of steel orother metal being forged.

Many of these difficulties and problems may be overcome by adoptinginduction heating as a substitute for furnace heating. The formation ofscale is virtually eliminated, substantially uniform heating can beobtained, and the time of heating is reduced substantially. On the otherhand, the power required for heating is relatively high, and the heatingequipment, which operates at relatively high frequencies, is quiteexpensive. An even greater disadvantage is presented by the coils usedfor induction heating. Coils which are efficient for a large billet arenot efficient for smaller pieces, and, of course, coils used for smallbillets cannot be employed with large pieces.

It is a primary object of the invention, therefore, to provide a new andimproved method of forging, and particularly of pie-heating a billet inthe course of a forging operation, which effectively eliminates theabovenoted difficulties and disadvantages of previously known methods.

A more specific object of the invention is to provide a practical andeffective method of pro-heating a billet, during a forging operation,which avoids the formation of scale on the billet, heats the billetuniformly, and may be accomplished almost instantaneously.

Another object of the invention is to afford a new and improved forgingmethod in which the billet is directly electrically heated, which methodis readily and conveniently adaptable to either manual or automatichandling of the billet during all stages of the forging operation.

A further object of the invention is a new and improved forging methodin which a billet to be forged is directly heated, by resistanceheating, before the final 3,059,535 Patented Dec. 18, 1962 forging step,which method is applicable to all kinds and types of steel susceptibleto forging and may also be applied to other metals.

Another object of the invention is a new and improved automatic forgingsystem for preparing a billet, resistanceheating the billet, and forgingthe billet, which system is useful in connection with a wide variety ofbillet shapes formed of substantially different alloys.

The billets used in normal forging operations are not particularlyuniform in shape, they may vary substantially in cross-sectionalconfiguration, and the ends are fre quently rough and irregular. Thesevariations can be overcome by using special billet stock, and by specialcutoff methods, but these expedients are not normally economicallyfeasible. Consequently, it is difficult to pass large electricalcurrents through such billets without causing substantial damage to thecontact electrodes or welding the electrodes to the billet. Thispresents a substantial probiem in direct resistance-heating of thebillets, particularly steel billets, as is required in the method of thepresent invention. This problem can be overcome by machining specialcontact areas on the billets, in accordance with one aspect of themethod of the invention. On the other hand, it is desirable to eliminatethis special machining or other preparation operation on the billets ifpossible, because of the attendant expense and the time required.

A further object of the invention, therefore, is to provide for directelectrical heating of an irregularlyshaped billet, particularly a steelbillet, with a minimum of machining or other preparation of the billet.

Another object of the invention is to provide for preheating of abillet, in a forging operation, by a multiplecontact eiectrode structurewhich eliminates or minimizes contact arcing but is adaptable toautomatic handling of billets on a production-line basis.

A further object of the invention is to provide a multiplicity ofindividually movable contacts, in a single electrode structure, fordirect pre-heating of a billet in a forging operation, and at the sametime to provide for cooling of all of the contact members by water orother liquid coolant.

Other and further objects of the present invention will be apparent fromthe following description and claims and are illustrated in theaccompanying drawings, which, by way of illustration, show a preferredembodiment of the present invention and the principles thereof and whatI now consider to be the best mode in which I have contemplated applyingthese principles. Other embodiments of the invention embodying the sameor equivalent principles may be used and structural changes may be madeas desired by those skilled in the art without departing from thepresent invention and the purview of the appended claims.

In the drawings:

FEGURE 1 is a partially schematic illustration, partly in perspective,of a. forging system constructed in accordance with one embodiment ofthe invention, and is used to explain the inventive method;

FIG. 2 is a detail view illustrating one technique for securinelectrical contacts to a billet for direct resistance heating as a partof a forging operation;

FIG. 3 is a further detail view showing another method of applyingelectrodes to a billet;

FIG. 4 is a sectional end elevation view of an electrode construction,in accordance with one feature of the invention, providing for directelectrical heating of irregularly shaped billets; and

FIG. 5 is a sectional side elevation view of the electrode fixture ofFIG. 4, taken approximately along line 5-5 in FIG. 4. t

The forging system illustrated in FIG. 1 comprises three major stages ofoperation, the billet preparation station 10, the heating station 11,and the final forging station 12. The three stations are preferablyinterconnected to form an integrated automated system, the interstageconnections comprising the conveyor 13 connecting the preparationstation to the pro-heat station 11, and the conveyor 14 connecting theheating station to the final forging station 12,.

The billet preparation station 1t) is utilized to prepare the billetsfor the electrical heating to be effected in the station 11.Accordingly, the station 19 includes suitable apparatus for forming apair of smooth, scale-free, rustfree contact areas on each of thebillets before they are fed to the conveyor 13 and thence into thestation 11. Preferably, the contact areas are formed at the extreme endsof the billet, in each instance, but other locations may be selected ifdesired. In fact, in upset forging, it may be desirable in at least someinstances to form the contact areas at intermediate points on thebillets, so that the end portions, or at least one end portion, of each"billet is not heated to the same extent as the central part of thebillet. In any event, however, it is necessary to prepare two spacedportions of each billet for contact with the electrodes of the heatingapparatus described hereinafter in connection with station 11.

The billet preparation station 1% includes a magazine 15 in which asupply of billets 13 are stored. From the magazine 15, the billets arefed one-by-one to a preparation apparatus 19; any suitable means may beemployed to feed the billets into the apparatus 19, depending upon thesize of the billets, the rate of feed, and other factors. In theapparatus 19, the billets are advanced past a pair of grinding wheels 16and 17, which are located at opposite sides of the apparatus in positionto engage the end portions of the billets. The preparation apparatus 19also includes a conveyor 21 or other suitable apparatus for moving thebillets through the preparation station and one or more hold-downmembers 22 for maintaining the billets in alignment with the grindingwheels 16 and 17 during the grinding operation. The grinding wheels maybe pivotally mounted, with respect to the conveyor 21, to provide formovement between an inactive position displaced from the billets 18 onthe conveyor and a grinding position in which the wheels engage thebillets and grind smooth contact surfaces 23 and 24, on the opposite endportions thereof.

From the conveyor 21 of the preparation station 10 the billets 18 aretransferred to the conveyor 13 connecting the preparation apparatus 1?to the heating station 11. The conveyor 21 may be operated continuouslyor intermittently, depending in part upon the particular constructionand arrangement employed for the grinding apparatus, and the same may betrue of the interstage conveyor 13. Preferably, however, the conveyor 13is operated continuously and feeds the prepared billets into a storagemagazine 25 in the heating station 11 of the forging system.

In the heating station 11, the prepared billets 18 are fed from thestorage magazine 25, sequentially, into a heating position in which theyare engaged by a pair of electrode structures 26 and 27, as illustratedby the billet 18A. Each of the devices 26 and 27 comprises a relativelylarge electrode capable of carrying very high heating currents for atleast short periods of time. The

I electrode 27 engages the prepared contact portion 23 of the billet,Whereas the electrode 26 engages the prepared contact surface 24. Theelectrodes should be constructed from an alloy having a relatively highconductivity, but capable of withstanding relatively high temperatures,particularly at the contact faces. Certain beryllium-copper alloys areconsidered to be suitable for this purpose, but no one alloy is ofcritical importance in this regard. The electrodes may be faced with arelatively hard metal, including some steel alloys, if desired, toreduce the wear normally experienced at the contact face; in manyinstances, however, this may not be desirable because it increases thepossibility of welding the electrode and billet together in the eventarcing occurs during the heating operation. in the illustratedarrangement, each of the electrode structures 26 and 27 is constructedas a movablejaw clamp, but other constructions may be utilized,including those described hereinafter, in connection with Fl 13. 2 and3.

10 The two electrodes 25 and 27 are connected to an electrical controlunit 28. The control unit is in many respects similar to the controlapparatus for a resistance welder, except that provision is made to cutoff the current applied to the two electrodes in accordance wit 5 thetemperature of the billet MA, instead of being based upon fixed timeintervals or other control criteria. A

ing device is provided to actuate the control ap- ".15 2,3. The sensingdevice 29 may be a device which cctly actuated by changes intemperature, or may 20 comprise photoelectric device sensitive to lightof a specific color, in which case the control of the apparatus "s maderesponsive to changes in the color of the billet 18A as its temperatureincreases. Of course, the control .pp tus is connected to a suitablepower supply,

as a 220 v. or 446 v. 60 cycle supply.

As noted hereinafter, the billet 18A is heated to a temperature of theorder of 2000 or more during the time that it is engaged by theelectrodes 22:; and 27, with the result that the electrodes tend to heatup to a corre- 30 spending high temperature. To hold the electrodetemperature as low as possible, the electrodes are preferably providedwith internal passageways and are connected to a source of coolant, hereshown as the water supply 31. Of course, suitable precautions must betaken to 3D prevent shorting out of the electrical system through thewater supply, but this is not a particularly difficult problem since theelectrodes are operated at relatively low voltages and the billet 18A isa much better conductor than the stream of water flowing through theelectrodes from the water supply 31. Other coolants may be used ifdesired, or air cooling could be utilized, but Water cooling is usuallythe least expensive and most effective arrangement.

From the heating station 11 the heated billets are transferred along theconveyor 14- into the forging station 12. A typical forging press 32 isillustrated in FIG. 1, and comprises a heavy frame 33 which is used tosupport a ram 34 above a bolster 35. Suitable forging dies may bemounted upon the bolster in the usual manner. The forging press 32 alsoincludes an operating mechanism, including a flywheel 36, for drivingthe ram 34 downwardly toward the bolster 35 to effect a forgingoperation; inasmuch as operating mechanism of this kind is well known inthe art, the mechanism is not shown in detail in the drawings.Preferably, an electrical control system is provided for the press 32,including a control treadle 37 for operating the press. On the otherhand, in a fully automatic system the press may be arranged for remote6Q control from a distant location or may even be provided with controlapparatus capable of actuating the press in response to delivery of abillet to the dies on the bolster 35.

In feeding the heated billets to the forging press 32 at the forgingstation 12, the conveyor 14 feeds each billet 5 through the window 38 atthe left-hand side of the press as seen in FIG. 1. In an automaticsystem, the completed forgin gs are usually removed from the pressthrough the window 39 at the opposite side of the press, but theforgings may also be removed from the front or, more usually, the backof the press.

In carrying out the forging method of the invention, three major stepsare effected in sequence, one step being completed in each of the threemain operating stations 19, 11 and 12 of the system of FIG. 1. In thefollowing discussion, these three major steps are considered in theiraccuses order of occurrence, certain variations and modifications ineach step being set forth along with the basic requirements of thatstep.

As noted hereinabove, the first step in the method of the presentinvention is the preparation of the billet. In most instances, thispreparation comprises the formation of a pair of spaced, smooth, cleancontact surfaces on the billet. The arrangement illustrated in FIG. 1,in which individual contact areas are formed in the billet by grindingor otherwise machining the billet, is exemplary of this step of themethod, and affords clean, smooth surfaces which may be engaged by theelectrodes 26 and 2,7 with a minimum or arcing. In the illustratedarrangement, the contact areas 23 and 24 comprise annular bands locatedat the ends of the billets, and this is an advantageous technique whichprovides for convenient engagement by the electrodes and affords uniformcurrent distribution, and hence uniform heating, throughoutsubstantially the entire body of the billet. On the other hand, thegrinding or other surface-machining apparatus of station may be arrangedto finish the ends of the billets into parallel, smooth, planarsurfaces. If this is done, the resulting contact surfaces may be engagedby planar electrodes arranged for reciprocating movement in a directionnormal to the planes of the contact surfaces when the billet is disposedin the heating station 11 in position to be heated. Other variations inthe configuration of machined contact surfaces, such as the surfaces 23and 2.4, are discussed hereinafter in connection with FIGS. 2 and 3.

In some instances, it may not be necessary or particularly desirable tomachine the billets in the preparation stage of the forging operation.This is particularly true if the electrodes used in the heating station11 are constructed to accommodate substantial variations in billetconfiguration, as with the electrode construction described hereinafterin connection with FIGS. 4 and 5. On the other hand, it is usuallynecessary to make sure that the billet surfaces to be contacted by theelectrodes of the heating station are clean and free from rust or scale.For this purpose, the preparation station 10 may be used primarily toclean the billet, either mechanically as by a light grinding operationor other abrading operation, or by use of solvents and other chemicalcleaning means, or both. Thus, the degree of preparation necessary inthe initial stage 10 of the forging system is to some extent dependentupon the heating apparatus employed and the particular method selectedfor applying the heating current to the billets.

In heating the billets, as noted hereinabove, a relatively large currentis passed through each billet for a short period of time to heat thebillet uniformly throughout its cross-sectional area. For steel billets,the forging temperature is usually of the order of 2000 F. to 2300 F.,the optimum forging temperature varying to some extent with differenttypes of steel. Itis usually desirable to raise the steel from ambientto forging temperature in a very short time interval, usually of theorder of one minute or less. To achieve this result, current densitiesof the order of 10,000 amperes per square inch must be achieved.Consequently, and as noted hereinabove, it is essential to achieve goodcontact between the electrodes 26 and 27 and the contact areas 23 and 24of the billets. Preferably, the electrodes are pressed firmly againstthe billets, and are made as nearly identical in configuration to thebillet contact surfaces as possible.

FIG. 2 illustrates another contact-electrode configuration which may beused in carrying out the method of the invention. In this arrangement,the billet 48 is machined to afford a chamfer 49 on the end thereof, asimilar chamfer being formed on the opposite end of the billet (notshown). The bevelled contact surface 49 may also be formed by coldchamfering in a press. The electrode' in this instance is constructed asindicated by the electrode 51, which is provided with a recess 52 forreceiving the end of the billet 48, the recess 52 having an internalinclined contact wall 53 which matches the chamfer 49. During heating,the electrode is forced against the end of the billet 48 is indicated bythe arrow 54 to assure good contact between the contact wall 53 and thebillet contact surface 49.

Another electrode arrangement is shown in FIG. 3. Here, the billet 53 isprovided with two flat contact surfaces 56 and 57 which are locatedopposite one another near one end of the billet. Two contact blocks 61and 62 are engaged with the contact surfaces 57 and 56, respectively,being forced inwardly toward each other and toward the contact surfacesas indicated by the arrows 63 and 64. The two contact blocks s1 and 62are electrically connected to each other to form a single electrodestructure. A similar arrangement may be employed at the opposite end ofthe billet 58. In this arrangement, it should be noted that the extremeend 65 of the billet 58 carries no current, and therefore is not heatedto the same extent as the center portion of the billet, an arrangementwhich may be desirable. in some forging operations, particularly upsetforging. On the other hand, if the flat contact surfaces 56 and 57 arelocated at the extreme end of the billet, the end portion of the billetcan be heated to full forging temperature along with the rest of thebillet.

In a typical heating installation, the control unit 28 may have a ratingof 300 kva., may provide current densities in the. steel billets ofabout 10 ,000 amperes per square inch, and may be capable of heating2000 lbs. of steel, to 2300" F, per hour. The heating apparatus maycomprise single-phase electrical equipment, but may also constitute athree-phase apparatus. In the latter instance, each phase is connectedto a separate pair of electrodes, thus affording three different heatingset-ups, which may be employed to feed three different forging stationsor may be utilized in heating billets for a single press, upsetter, orhammer. It should be noted that most forging equipment can be maintainedin continuous operation on an input of 3000 lbs. per hour or less.

Because the billets fed to the press 32 are all uniformly heated to acontrolled temperature, the press may be readily and conveniently madealmost wholly automatic in operation. The heated billets are fed throughthe window 38 into the first die section on the bolster 35. Provisionmay be made for automatically transferring the billets between diesafter a given number of impacts by the ram 34 and for automaticallyremoving the finished forging without any control operation on the partof an operator. In fact, in most instances all variable quantities maybe considered to be eliminated.

FIGS. 4 and 5 illustrate a contact construction which may be used tosubstantial advantage in connection with the forging method of thepresent invention. The apparatus shown in these two figures comprises afirst electrode structure 71 and a second electrode structure 72 whichare utilized in heating a billet 73. The billet is eifectively clampedbetween the two electrode structures, which cooperate to pass a heatingcurrent through the billet in a transverse direction, instead oflengthwise thereof, as de scribed more fully hereinafter.

The electrode structure 71 comprises a mounting member or base 74 whichis substantially U-shaped in cross section, as shown in FIG. 4, andwhich is provided with a pair of end plates 75 as illustrated in FIG. 5.Within the confined space defined by the base and end members there aremounted a multiplicity of individual electrode or contact elements, andit is these contact elements which engage the billets. In theillustrated construction there are three individual contact elements ineach layer, as shown by the contact elements 76, 77, and 78 in FIG. 4.The longitudinal arrangement of the multiple layers of contacts is shownin FIG. 5 by the contact elements 77, 77A, 77B, 77C, 77D, etc.

Lateral movement of the contact elements such as the contacts 76-78 isprevented by engagement of the contact elements with the sides of thebase 74 and with each other.

Longitudinal movement within the base is prevented by engagement of thestacks of contacts with the end walls 75 of the electrode structure 71.The contacts are free to move, to a limited extent, in a verticaldirection, each contact being independently movable in this directionwith respect to the base 74 and each other. Upward movement of thecontacts 76 and 78 is limited by a pair of guide rails 80 and 82,respectively, which are mounted on the. inside of the opposite sidewalls of the U-shaped base 74, movement in the opposite direction beinglimited by engagement with the bight portion of the base. The centralcontact elements, such as the contact 77, may be held to a limited rangeof movement by suitable means such as a guide rod 83 extending betweenthe end plates 75 and through a series of elongated apertures 84- inthese contact elements.

The two exterior contact elements 75 and 78 are provided with bevelledor inclined contact surfaces 86 and 88, respectively, which extendinwardly toward each other to form a substantially \l-shaped notch, thebase of which is cut oh by the central contact element '77. The billet73 is disposed within this notch, during heating, in a notch of similarconfiguration formed by the contact elements )6, 97, and Q2? of theelectrode structure 72. The electrode structure 72 is essentiallysimilar to the electrode structure 71, and comprises a base for mountingthe contact elements and suitable guide means such as the guide rails91, 92, and 93 for limiting movements of the individual contact elementswith respect to the base and each other.

A bellows Mil is mounted in the base 7 4 of the electrode structure 71and engages the base surface of each of the electrode segments such asthe contact members 7548. The bellows ltil is provided with an inletconduit 162 at one end thereof, and an outlet conduit 3 33: is connectedto the opposite end of the bellows. The bellows ltlil is of the type towhich fluid may be applied, under pressure, with a restricted flowthrough the bellows being permitted but, at the same time, a build-up ofpressure within the bellows being achieved. Bellows structures of thiskind are known in the art, and, therefore, the complete construction ofthe bellows need not be shown in detail herein. By way of example, thedesired effect of permitting fluid flow through the bellows andaffording a build-up of pressure therein can be obtained byincorporating a normally-closed pressure-sensitive control valve in theoutlet conduit 1tl3, the valve being adjusted to open and permit a flowof fluid from the bellows once a predetermined pressure has beenachieved within the bellows. A similar bellows res is incorporated inthe electrode structure '72..

To facilitate operation of the heating equipment in which the electrodestructures 7 and 72 are incorporated, at least one of the electrodestructures is preferably mounted for reciprocating movement toward andaway from the other, as indicated by the arrows H6 in FIG. 4. Inoperation, the two electrode structures are first separated from eachother by a distance suliicient to permit convenient insertion of thebillet 73 therebetween. The electrode structures are then moved togetherto bring the contact elements of both electrodes approximately intoengagement with the billet. Fluid, usually water, is applied to the twobellows N1 and res, under pressure, building up the pressure within thebellows and forcing each of the contact elements of the two electrodestructures into contact with the billet. Since each element of themulti-element contact assemblies is individually movable with respect tothe others, each contact element such as the contacts 76-78 and %9S isforced into intimate contact with the billet, affording a relativelylarge total contact area on each side of the billet.

The two electrode structures are then energized, usually from a 60 cycleA.C. source as described hereinabove, to eifect a current flow ofsubstantial magnitude through the billet 73. Heating is ef ected inessentially the same manner as described in connection with FIG. 1,

except that the heating current flows across the bar or billet 73instead of longitudinally therethrough. To achieve the high currentdensities needed for heating to forging temperature in the desired shorttime, the total current required with the side or transverse heatingarrangement of FIGS. 4 and 5 is substantially higher than with theend-heating arrangement of FIG. 1. On the other hand, the totalresistance of the current path is lower, and much lower operatingvoltages can be employed.

The electrode arrangement of FIGS. 4- and 5 reduces the preparationnecessary for adequate heating without excessive arcing to a minimum,since the electrode structures effectively compensate for substantialirregularities in the surface of the billet. The electrodes 71 and 72can accommodate billets of various sizes, both as regards length,diameter, and cross sectional configuration. The described bellowsarrangement provides for cooling of the electrode structures, by meansof the water flowing through the bellows, and at the same time affordsan efiective and etlicient pressure or spring-like means for forcingeach of the multiplicity of individual contact elements into contactwith the billet to be heated. This coupled with the ability of eachcontact to seat independently on the billet enables the contactsindividually to conform to the contour of billet, thereby assuringeffective electrical contact with and heating of the billet. it shouldbe noted that there need not be three contact elements in each layer;two or four or more contacts per layer may be employed, and the ratio ofcontacts in each row need not be one-for-one, but may be varied ifdesired. The electrode structures are readily adaptable to automatichandling of the billets as they are fed into and out of the heatingstation of the forging system. The large number of contact areasprovided by each electrode structure reduces arcing to a minimum.

From the foregoing descript on, it is seen that the method of theinvention eliminates the formation of scale, since the billets areheated uniformly throughout the desired portion of their length withinan extremely short period. Heating is more uniform than with furnaceheating, and also more uniform than with induction heating, since theskin-effect prevalent at the high frequencies used for induction heatingdoes not occur to any substantial extent with direct resistance heating.Further, the invention provides faster heating than is practicable orpossible with either furnace or induction heating. The method of theinvention is adaptable to a, relatively slow, manually controlledforging system, but may be used to best advantage in an automatichigh-speed system. Further, it permits the use of a single automaticsystem for billets of various sizes and shapes with a minimum ofchangeover in equipment. In the forging of steel, particularly, themethod and system of the invention permit improved precision control ofthe forging operation without material increase in cost and usually at asubstantial reduction in cost.

Thus, while I have illustrated and described the preferred embodiment ofmy invention, it is to be understood that this is capable of variationand modification, and I therefore do not wish to be limited to theprecise details set forth, but desire to avail myself of such changesand alterations as fall within the purview of the following claims.

I claim:

1. in a forging system in which steel billets are directly electricallyheated to forging temperature by passing large, low-frequency electricalcurrents therethrough, an electrode structure for engaging a billet toprovide for heating the billet, comprising: a base structure defining aconfined electrode-receiving space open at one side; a multiplicity ofindividual contact elements movably mounted within said confined spaceand externally accessible at said one side of said base structure, saidcontact elements defining a substantially V-shaped notch for receiving abillet; means for limiting movement of said contact elements to movementtoward and away from said notch; a bellows device, mounted within saidbase structure in engagement with said contact members; and means forapplying fluid under pressure to said bellows device to force saidcontact elements, independently of each other, into contact with saidbillet.

2. In a forging system in which steel billets are directly electricallyheated to forging temperature by passing large, low-frequency electricalcurrents therethrough, an elec trode structure for engaging a billet toprovide for heating the billet, comprising: a base structure defining aconfined electrode-receiving space open at one side; a multiplicity ofindividual contact elements movably mounted within said confined spaceand externally accessible at said one side of said base structure, saidcontact elements defining a substantially V-shaped notch for receiving abillet; means for limiting movement of said contact elements to movementtoward and away from said notch; a bellows device, mounted within saidbase structure in engagement with said contact members, including meansfor limiting the fiow of fluid through said bellows; and means forapplying water under pressure to said bellows device to force saidcontact elements, independently of each other, into conductive contactwith said billet and to establish a flow of water through said bellowsto cool said electrode structure.

3. In a forging system in which steel billets are directly electricallyheated to forging temperature by passing large, low-frequency electricalcurrents therethrough, an electrode structure for engaging a billet toprovide for heating the billet, comprising: a base structure defining aconfined electrode-receiving space open at one side; a multiplicity ofindividual contact elements movably mounted within said confined spaceto form a laminated contact structure externally accessible at said oneside of said base structure, said contact elements defining a truncatedV-shaped notch for receiving a billet, each layer of said laminatedcontact structure including at least three individual contact elements;means for limiting movement of said contact elements to movement towardand away from said notch; a bellows device, mounted within said basestructure in engagement with said con tact members; and means forapplying water under pressure to said bellows device to force saidcontact elements, independently of each other, into contact with saidbillet, and to cool said electrode structure.

4. In a forging system in which steel billets are directly electricallyheated to forging temperature by passing large, low-frequency electricalcurrents therethrough, an electrode structure for engaging a billet toprovide for heating the billet, comprising: a base structure comprisinga U-shaped base and end plates defining a confined electrode-receivingspace open at one side; a multiplicity of individual contact elementsmovably mounted within said confined space and externally accessible atsaid one side of said base structure, said contact elements defining asubstantially V-shaped notch for receiving a billet; means for limitingmovement of said contact elements to movement toward and away from saidnotch within a narrow range; a restricted-flow bellows device, mountedWithin said base structure in engagement with each of said contactmembers; and means for applying fluid under pressure to said bellowsdevice to force said contact elements, independently of each other, intocontact with said billet, and to establish a cooling fiow of fluidthrough said bellows.

5. In a forging system in which steel billets are directly electricallyheated by passing large, low-frequency electrical currents therethrough,a pair of electrode structures for engaging a billet to provide forheating the billet, each of said structures comprising: a base structuredefining a confined electrode-receiving space open at one side; amultiplicity of individual contact elements movably mounted within saidconfined space and externally accessible at said one side of said basestructure, said contact elements defining a notch for receiving billetsof varying sizes and establishing electrical contact therewith at aseries of points along the length of any given billet; means forlimiting movement of said contact elements to movement toward and wayfrom said notch within a narrow range; a bellows device, mounted withinsaid base structure in engagement with said contact members; and meansfor applying fluid under pressure to said bellows device to force saidcontact elements, independently of each other, into contact with saidbillet.

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